Romain Grosjean admitted he made "a stupid mistake" in running in to Mark Webber at the start of the Japanese Grand Prix.

Webber branded Grosjean a "first-lap nutcase" after being tapped in to a spin by the Lotus in turn two at the start. The incident comes two races after Grosjean was banned from the Italian Grand Prix for causing a first-corner crash in Spa, and he admitted that he had tried to be careful since then but had been caught out by the closing speed as Webber slowed for the second corner.

"Ever since I came back in Singapore my priority has been to be very cautious at the start, and I was watching Sergio [Perez] on my left to make sure there was no contact with him," Grosjean said. "There was quite a big speed difference between me and Mark [Webber] as I came into the first corner which caught me by surprise and we collided. It was a stupid mistake."

Grosjean also revealed that Webber confronted him over the incident after the race and said he would look to learn from the error.

"Mark [Webber] came to see me after the race and was obviously not happy, but I apologised and we have to move on. We'll sit down and look at things again before the next race to see what we can do to improve these situations. In the last few laps of the race the tyres were at the end of their life and we were out of the points, so it made sense to retire. Not a good day, but we have to look ahead to Korea and a chance to make amends."